EFFECTS OF AGGREGATE SEAL COATS ON SKID INDEX NUMBERS & ACCIDENT RATES OF LOW VOLUME ROADS IN UTAH
Friction deficient sections of highway exist, and sometimes contribute to elevated accident rates. Agencies address this problem by applying friction courses to deficient roadway sections. This paper examines whether chip seal friction courses are an effective accident countermeasure on low volume, rural highways. This was accomplished by looking at chip sealing operations in District 3 of the Utah Department of Transportation. Data from this district indicate that there is no definite relationship between accident rates and skid numbers on roads that were chip sealed. The general trend was a decrease in the accident rate with an increase in skid numbers. However, the linear and non-linear relationships found in previous studies were not appropriate to describe the observed trend. On the assumption that the relationship between accident rate and skid number is non-linear, accident rate reduction after the application of a chip seal surface treatment was calculated using three methods. The first two methods did not consider the change in skid number. These two methods, estimated average reductions in accident rate of 63% and 61%, respectively. However, when the before and after treatment accident rates were compared, differences were found to be statistically significant at levels below 85%. This suggests that the expected reductions will be lower than the above estimates. The third method is more hypothetical. It produced an estimated average accident reduction of 39%.
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- This study was funded by the Utah Department of Transportation and the U.S. Department of Transportation's University Transportation Centers Program through the Mountain-Plains Consortium.
Fargo, ND United States 58108
- Seneviratne, P N
- Bergener, J M
- Publication Date: 1994-5
- Media Type: Digital/other
- Features: Appendices; Figures; References; Tables;
- Pagination: 39 p.
- TRT Terms: Before and after studies; Chip seals; Countermeasures; Crash rates; Friction course; Friction materials; Low volume roads; Rural highways; Safety; Seal coats; Skidding; Traffic safety
- Uncontrolled Terms: Skid number
- Geographic Terms: Utah
- Subject Areas: Design; Highways; Pavements; Safety and Human Factors; I22: Design of Pavements, Railways and Guideways; I23: Properties of Road Surfaces; I81: Accident Statistics;
- Accession Number: 00669028
- Record Type: Publication
- Report/Paper Numbers: MPC Rept No. 94-33
- Files: TRIS
- Created Date: Nov 23 1994 12:00AM